Electrophysiology catheters are commonly used for mapping electrical activity in a heart. Electrophysiology is a specialty within the field of cardiology for diagnosis and treatment of electrical abnormalities of the heart. By mapping the electrical activity in the heart, ectopic sites of electrical activation or other electrical activation pathways that contribute to heart malfunctions may be detected. This type of information may then allow a cardiologist to intervene and destroy the malfunctioning heart tissues. Such destruction of heart tissue is typically performed using an ablation catheter and is referred to as ablation. Ablation is a rapidly growing field within electrophysiology and obviates the need for maximally invasive open heart surgery.
Occasionally, an electrical abnormality occurs in a location that is difficult to reach with standard catheter capabilities. A left atrium of a heart is one such location. When an electrical abnormality occurs in a left atrium, a dilation catheter, or dilator, may be inserted percutaneously, fed through one or more major blood vessels, and inserted into a right atrium of the heart. A needle may then be feed through the dilator and inserted into and through the atrial septum to puncture the atrial septum to allow access to the left atrium for a therapeutic catheter, such as an ablation catheter.
A current technique for puncturing the atrial septum includes positioning a dilator adjacent to an area of the atrial septum that is desired to be punctured (typically at the fosa ovalis), inserting a separate needle into the dilator, feeding the needle through the dilator until the needle protrudes beyond the dilator, and puncturing the atrial septum with the needle. This technique has several disadvantages. For example, locating the desired puncture site and then inserting and feeding a separate needle into the dilator increases the procedure time, and increases the likelihood that the dilator will be inadvertently moved before the needle reaches the desired puncture site, thus requiring a repositioning of the dilator. If the repositioning is performed with the needle inside the dilator, the possibility exists for the needle to slide out of the dilator and damage venous or atrial structures. If the needle is removed during repositioning, procedure time is again extended during reinsertion and re-feeding of the needle into the dilator, and an inadvertent movement of the dilator during reinsertion and re-feeding of the needle again exists.
Another more serious disadvantage of the current technique is that, to dilate the hole enough for a guiding sheath to fit through with the dilator, the sharp needle has to be advanced ten to twenty millimeters into the left atrium, which would bring the sharp edge dangerously close to the superior wall of the left atrium, which might result in perforation, especially if the left atrium is small. Moreover, a force in a distal direction is required to insert the needle into and through the atrial septum, yet there is no means for controlling the maximum protrusion of the needle from the dilator. As a result, a tendency is for the operator to continue to apply a forward force to the needle even after the needle has crossed the atrial septum, thus risking damage to venous or atrial structures in the left atria or even cardiac puncture if the needle protrudes too far from the dilator.
Yet another disadvantage of the existing technique is that, when the sheath is advanced into the left atrium, it is typically placed at least about ten millimeters beyond the septum wall. If it is advanced less than ten millimeters, it might fall out of the left atrium. This gives catheters and other devices that go through the sheath very limited access to the septum from the left side. If a procedure requires mapping or ablation on the left septum, it is almost impossible to perform with conventional sheaths.